Power Amplifiers for mm-Wave 5G Applications: Technology Comparisons and CMOS-SOI Demonstration Circuits

A review is presented of key power amplifier (PA) performance requirements for millimeter-wave 5G systems, along with a comparison of the potential of different semiconductor technologies for meeting those requirements. Output power, efficiency, and linearity considerations are highlighted, and related to semiconductor material characteristics. Prototype 5G PAs based on silicon technologies are then reviewed, with primary emphasis on CMOS-SOI. Stacked FET PAs based on nMOS and pMOS for 28-GHz operation are presented, along with outphasing and Doherty amplifiers. Peak power-added efficiency (PAE) up to 46% is demonstrated for a two-stack pMOS amplifier with saturation power (Psat) above 19 dBm. PAE at 6 dB backoff above 27% is shown for an nMOS Doherty PA with 22-dBm Psat. Operation with 64QAM OFDM modulation signals at 800-MHz bandwidth is reported, with up to 13-dBm output power and more than 17% PAE, without the use of digital predistortion. Future challenges for PA development are discussed.